1. Field of the Invention
The invention relates to a flame penetration blocker for fuselages and a method for its manufacture.
2. Description of Related Art
In a so-called post crash fire, i.e., upon the impact of aircraft on the ground and development of a fuel fire, the flame penetration time of a fuselage from outside to inside is only 30 to 60 seconds. Moreover, the melting point of the aluminum skin amounts to approximately 640.degree. C.; burning kerosine produces a temperature of over 1000.degree. C.
Presently, there are still no legal regulations which relate to the flame penetration behavior of an aircraft skin.
German patent application 26 05 102 describes a multilayered insulating material consisting of carrier material bonded with a curable or a cured plastic binding agent, mica paper and a cover material on the other side of the mica paper. The stated objective of this patent is to specify a high-temperature resistant insulating material which has an improved processability and winding properties, and in a wound state allows for a uniform full impregnation of a plurality of layers arranged one over another. This is achieved by arranging the binding agent in a pattern formed of points, diamonds or stripes.
Preferably, the addition of the hardener, and therewith the final cross-linking of the pre-crosslinked epoxy resin, is carried out with the following impregnation process. The carrier material is a formed fabric having adhesive substance imprinted in a pattern, which, after the drying, exists in pre-crosslinked state. Onto this, fine mica paper and a cover sheet made of a further formed fabric having corresponding adhesive substance imprint are laid on top of one another, and the entirety is intimately bonded in a heated calender. This version, in which the epoxy resin is still not finally cross-linked, is now wound to form a finished insulating body with hollow spaces, the mica sheets not breaking. This hollow body is penetratingly impregnated with an insulating resin to which is added a curing agent suitable for the binding agent. By this means, the final curing of the epoxy resin pattern-imprinted on the formed fabric is carried out simultaneously during the full impregnation.
In another non-wound version, the plastic binding agent of the insulating material is already cured.
Because of its geometric shape as a wound structure, the first version is not suitable for installation in fuselages. Because of the cured binding agent, the second version is stiff to such an extent that the structural irregularities of fuselages cannot be covered all over.
Therefore, this prior art is not suitable for increasing the flame penetration time of fuselages.
The German patent application 27 00 608 relates to a non-flammable composite insulating material composed of a core sheet A and two covering layers B. The core sheet A contains inorganic conductive particles which are bonded together by 1 to 30% by weight of a temperature resistant, high-molecular binding agent having a lasting service temperature in accordance with DIN 53 446 of more than 100.degree. C. The two covering layers B represent a flat carrier material of inorganic or organic fibers or wires bonded together, which are likewise bonded with 3 to 30% by weight of the named binding agent.
Because of the high content of binding agent in all the layers, such an insulating material is very stiff and is not able to conform all over to contoured opposite surfaces as they exist in large number in the fuselage. The completely cured binding agent is responsible for the stiffness of the composite insulating material.